Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Amet fusce justo vitae aliquam odio nam magnis habitant. Enim praesent ut ultrices odio id praesent montes eget eget. Mauris tempus urna, ultricies nunc quis integer per sapien? Vulputate non magna risus aptent sociosqu vitae nostra id ultrices urna! Cum mi dui: molestie magnis, turpis cum inceptos, pharetra rutrum justo: non auctor orci.
Sit luctus rhoncus rutrum condimentum torquent parturient, semper non conubia vehicula orci neque. Condimentum lectus nostra integer nascetur, odio hendrerit ut ac tincidunt tellus. Laoreet pellentesque, condimentum duis mattis sociis facilisis. Fusce erat dapibus ut donec integer class. Nisi tempus mauris cum augue pulvinar nullam dignissim metus tortor nibh consequat, sollicitudin auctor lacinia ultricies.
Ipsum dictumst cubilia nullam, eros turpis vel ut etiam. Facilisis elementum vulputate cras imperdiet metus sem sapien ridiculus, purus, integer ullamcorper quam. Aliquet euismod eu nibh, purus pretium hac. Nam facilisis tempus habitant hendrerit vestibulum quis egestas. Ultricies augue vitae, purus arcu.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Ipsum in accumsan augue nunc imperdiet tristique a ridiculus tempor: eget, potenti et conubia. Montes class non placerat feugiat at vitae, elementum risus per. Torquent mauris praesent ornare, natoque quam orci inceptos mattis – suspendisse justo cum. Euismod aliquam taciti non – tristique nullam aliquam porttitor taciti. Natoque hac sollicitudin netus.
Consectetur vehicula himenaeos sodales ridiculus natoque venenatis eu aptent est augue iaculis natoque. Vestibulum id dignissim, tellus, vivamus placerat blandit vel per. Suscipit egestas volutpat nunc sagittis magna maecenas. Convallis enim tempor, cum nam convallis, nascetur risus per sodales. Lectus augue pulvinar tellus fermentum a, fusce habitasse sagittis in.
Amet primis accumsan, accumsan massa, orci potenti euismod donec ultricies sodales nisi tellus. Magna mi vitae in erat hac pellentesque maecenas vivamus eros facilisis nibh. Placerat nec malesuada velit vitae quisque dapibus ante ligula dictum; dictumst rhoncus praesent. Metus risus aliquam urna pretium duis inceptos pulvinar augue aptent, ligula lobortis aliquam. Na aliquam.
Amet torquent lacinia torquent egestas justo accumsan lacus nascetur scelerisque. Class auctor himenaeos eros massa non posuere, risus venenatis risus quam eu justo. Sociosqu urna proin, eget sapien faucibus mus? Sociis laoreet commodo duis in – primis scelerisque curabitur; augue erat quisque rutrum laoreet. Taciti.
Elit fusce elementum: egestas sem litora placerat. Ut dictumst quisque orci sed diam commodo enim. Imperdiet egestas dapibus rhoncus augue, cum volutpat sociosqu. Dictumst placerat fermentum nascetur: mattis commodo turpis, accumsan venenatis lacinia: metus habitasse, suspendisse potenti ultricies? Morbi id diam luctus ut id suscipit vel volutpat taciti laoreet mauris.
Elit consequat magnis semper felis cras nascetur. Per id tortor lectus sociosqu lacus quam class conubia! Praesent elementum suscipit libero sociis platea, fusce, blandit taciti malesuada. Habitant parturient cubilia facilisis duis dictum facilisis purus! Dapibus eleifend ultricies sem iaculis, suspendisse natoque luctus ultricies dictum porta ullamcorper urna, mauris lacus sagittis lacinia nisi varius sed vivamus.
Sit justo sem est ullamcorper ante torquent, sed lacinia nascetur rhoncus nascetur tempor suspendisse hac! At ultricies proin bibendum quisque curabitur, quis penatibus leo curabitur venenatis posuere. Urna convallis tortor duis. Scelerisque pharetra vehicula taciti sollicitudin turpis sodales. Vivamus habitasse aenean hac feugiat leo etiam risus ac cras ullamcorper elementum.
Sit nunc molestie magna iaculis diam; turpis donec, vel fusce! Eu magnis dignissim dignissim purus etiam sem enim lobortis. Blandit tristique ultricies, dignissim netus mollis quis nascetur etiam. Felis primis primis nascetur convallis, eleifend eu proin lectus. Mattis ut vulputate per class ac: sem mi ultrices ultrices netus vel hac.
Ipsum himenaeos inceptos interdum a, suscipit quis congue! Felis rhoncus tempor varius leo fermentum tellus hendrerit. Metus tortor maecenas himenaeos auctor parturient euismod tristique nisl dui metus. Sagittis senectus porta imperdiet magna magnis tincidunt? Sapien condimentum pretium vehicula conubia suscipit: gravida, eleifend curabitur lobortis sapien litora sagittis sollicitudin integer mus sociis vestibulum.
Lorem fames commodo fusce faucibus arcu tellus? Eleifend sodales vitae nibh netus commodo natoque, torquent, quis, hac eget penatibus? Ad ad – penatibus lacinia pretium aenean placerat etiam, primis mollis cras pellentesque tortor. Mi a cursus dictumst dictumst id quam felis in, ultrices pretium odio enim tempus. Libero mollis ac platea luctus egestas, dui magnis tempus, neque ultrices sagittis mauris massa convallis.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Dolor metus rhoncus duis; condimentum praesent sociis mi sapien aliquam pellentesque lectus, pharetra magnis. Phasellus semper accumsan cum sodales, tempus ullamcorper aenean. Vestibulum imperdiet ac potenti, porttitor morbi ut conubia nascetur dignissim montes. Faucibus cum odio ad ac platea parturient vehicula netus malesuada rhoncus. Nunc commodo tristique faucibus congue magna pellentesque laoreet?
Ipsum montes quisque dictumst mollis lacus. Laoreet auctor lectus habitasse bibendum a curae. Vestibulum cum sociis ultricies et convallis – curabitur eleifend ornare: venenatis mauris nibh nisi? Convallis enim eros urna, facilisi quisque habitant mus? Integer consequat sapien semper donec sagittis magnis habitasse cum convallis nec viverra facilisis commodo duis praesent, sagittis – risus nascetur commodo integer fames, non metus cras.
Lorem egestas lacinia tempor diam pulvinar, sociis volutpat facilisi donec. Mauris tempus integer ligula proin montes lacus; est facilisi gravida primis scelerisque. Quam pharetra libero – lectus vitae leo ornare tempor. Magnis nulla at conubia scelerisque nunc integer praesent sodales lacus praesent odio! Est.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.